Really, I think most people have one litmus test or another when it comes to spoken grammar. A buddy of mine, for example, is especially sensitive to “reiterate vs. iterate” while my girlfriend is a sentinel of “lay vs. lie.” It’s hard to shake.

Here’s one I use for writers: Does he/she use the word “myriad” correctly? That’ll show you who’s a black belt.

People (Wikipedia) will try to sell you on the concept that both “myriad ideas” and “a myriad of ideas” are correct examples of usage. But I and others of my dojo say No! The noun form–myriad without “of/and”–is both the reigning standard and aesthetic superior, and shall be upheld. When we walk the streets and see members of the opposing dojo, we fight them.